/*这是注释：表示该文件支持UTF-8编码*/
@charset "utf-8";
#left{
    width: 480px;
    height: 1000px;
    position: fixed;/*固定定位*/
    left: 0px;
    top: 0px;
    background: url('../images/01-1.jpg')center -40px;
    background-size: cover;
    animation: loop 8s infinite step-end;
}
@keyframes loop{
    25%{background-image: url('../images/01-2.jpg');}
    50%{background-image: url('../images/01-3.jpg');}
    75%{background-image: url('../images/01-4.jpg');}
    100%{background-image: url('../images/01-1.jpg');}
}
#app{
    width: 480px;
    margin:100px auto 0;
    /*在原始位置相对左边80像素*/
    position: relative;
    left: 80px;
}
#face{
    width: 100px;
    height: 100px;
    border-radius: 50%;
}